The present invention relates to a disk recording and reproducing apparatus, and more particularly to a disk recording and reproducing apparatus which implements higher-speed rotation and higher-density data recording.
Further, the present invention relates to a disk recording and reproducing apparatus which corrects at least one of a squareness error and a misalignment on a disk recording and reproducing apparatus basis, which further allows such a correction to be made even on a disk-to-disk basis, and which still further allows the squareness to be automatically maintained at zero even in a high-double-speed disk recording and reproducing apparatus that rotates disks at high speeds.
Still further, the present invention relates to a disk recording and reproducing apparatus whose focus adjusting mechanism is downsized.
The principle of a disk recording and reproducing apparatus will be described briefly based on FIGS. 1 and 2. In FIGS. 1 and 2, an optical disk 1, such as a CD (Compact Disk) or a DVD (Digital Versatile Disk), is rotated about the shaft of a rotary body 3 by a spindle motor 5. A pickup 7 is provided in order to irradiate the signal recording surface of the disk 1 with a laser beam and to receive the laser beam reflected by the signal recording surface. "Squareness" means a deviation value (or a nominal value of the squareness every predetermined time) obtained when the angle formed between the optical axis 9 of the laser beam irradiated from the pickup 7 and a predetermined range of the recording surface of the disk 1 is out of 90 degrees.
On the other hand, in order to search for certain pieces of data recorded on the disk 1, the pickup 7 is moved along a guide rail (not shown) in such a manner that the pickup 7 moves in parallel with the disk 1 and the optical axis 9 of the laser beam is directed toward the outer circumference from the inner circumference of the disk 1. During this movement of the pickup 7, it is ideal for the center of curvature 11 of signal tracks formed on the recording surface of the disk 1 to be positioned on an extension of the locus of movement of a point at which the optical axis 9 of the laser beam crosses the recording surface of the disk 1. It occurs, however, that the center of curvature 11 is out of position (hereinafter referred to as "misalignment") due to problems encountered when the apparatus is manufactured and the like.
The term "misalignment" is defined as a distance between the extension of the locus of movement of the point at which the optical axis 9 of the laser beam crosses the recording surface of the disk 1 and the center of curvature 11 of the signal tracks formed on the recording surface of the disk 1. In order to make correct signal recordings and/or signal readings, values of squareness and misalignment are required to be maintained within their tolerances.
To meet this requirement, a conventional disk recording and reproducing apparatus is constructed as follows. A tilt adjusting mechanism 13, such as shown in FIG. 3, is provided on a table of the spindle motor 5, and the mechanism 13 is adjusted during the manufacturing process. Alternatively a tilt servo control means for controlling the direction of both the whole pickup 7 and its guide rail and the like is provided. The tilt servo control means maintains the squareness at zero by detecting the squareness while signal recordings and/or signal readings are being made. Further, a misalignment adjusting mechanism (not shown) for adjusting the direction of the guide rail of the pickup 7 is also provided, and this mechanism is adjusted during the manufacturing process.
However, there has been the disadvantage that the conventional tilt adjusting mechanism 13 and misalignment adjusting mechanism can correct squareness errors and misalignments caused by profile errors and assembling errors of the rotating mechanical parts of the disk 1 and of the driving mechanical parts of the pickup 7 on a disk recording and reproducing apparatus basis, but squareness errors and misalignments caused by the warpage of a disk and eccentricity of the center hole and of the center of curvature of the signal tracks cannot be corrected.
Further, since the conventional tilt servo control means has to change the direction of the whole pickup 7 and the direction of the guide rail of the pickup 7 and the like, it needs to handle a large inertia of its controlling object, and hence the response of its control system is slow. Therefore, in a high-double-speed disk recording and reproducing apparatus that rotates disks at high speeds, there arises the disadvantage that such means does not allow the squareness to be automatically maintained at zero.
On the other hand, FIG. 4 is a schematic conceptual diagram showing the whole conventional disk recording and reproducing apparatus. Further, FIG. 5 is a schematic diagram showing the construction of a disk that allows data to be recorded and reproduced in two layers in one direction. The disk 1 has data recording layers 14 and 15 within its translucent film 12. A disk type determination/switching/reading unit 37 can determine the type of a disk, such as a CD or a DVD, to switch modes and reproduce data recorded on the disk.
The disk 1 is driven to rotate by the motor 5 through the rotary body 3. The rpm of the rotary body 3 is adjusted by a rotary servo 25. The pickup 7 irradiates the data recording layers 14 and 15 with a laser beam, and receives the laser beam reflected by the recording surface of these data recording layers 14 and 15.
Generally, in the conventional disk recording and reproducing apparatus, in order to read data recorded on the disk 1, the focus of the pickup 7 needs to be adjusted as shown in FIG. 5, and thus a focus servo actuator 21 is provided in the pickup 7 to implement such a focus adjustment.
Further, in order to read the data on the disk 1, a tracking servo actuator 24 is also required to be provided. The actuator 24 serves to move the objective lens of the pickup 7 in the radial direction of the disk 1. Thus, the pickup 7 has two types of actuators, the actuators 21 and 24.
Still further, the fact that the pickup 7 incorporates therein two actuators has imposed the problems, e.g., that it is hard to downsize the apparatus and that measures against heat derived from the actuators needs to be taken.
Still further, the conventional disk recording and reproducing apparatus uses bearings, such as ball bearings, which come in mechanical contact with the rotary body 3 for supporting the rotary body 3 arranged at the center of the disk 1, and this has prevented the disk 1 from rotating at a very high speed.
Still further, when bearings such as ball bearings involving mechanical contact are used, the rotary body 3 is subjected to deflections caused by its rotation due to, e.g., the fact that the rotary body 3 is out of balance and that there is a clearance between the rotary body 3 and the bearing.
A solution to these problems could be the use of bearings such as gaseous bearings, so that mechanical contact can be avoided.
However, even when gaseous bearings are used, a problem is still addressed in that the bearing of this type is hard to be controlled actively unlike a bearing utilizing a magnetic force. For this reason, the use of gaseous bearings gives no substantial improvement for the deflection of the rotary body 3 compared with the use of bearings involving mechanical contact such as ball bearings. Thus, even with the use of gaseous bearings, the deflection of the rotary body 3 and the like still impose the problem that the data recording density cannot be improved.